Method of controlling foam with carbonic acid ester agents

ABSTRACT

Methods of use of carbonic acid esters corresponding to general formula I: ##STR1## in which R 1  is an alkyl radical derived from an aliphatic saturated primary alcohol containing 1 to 22 carbon atoms and R 2  is an alkyl radical derived from an aliphatic, saturated primary alcohol containing 1 to 8 carbon atoms and/or has the same meaning as R 1  and n is a number of 2 to 20 while m is 0 or has the same meaning as n, as foam control agents for the sugar beet or potato-processing food industry and/or in fermentation processes are provided. In the industrial processing of sugar-containing plant juices, as carried out on an industrial scale in the case of sugar beet, particular difficulties are caused by excessive foaming in the defecation units, during transport of the beet, in the diffusors and in the carbonizing tanks and before the evaporators, thus, use of the esters in these processes is advantageous. Other areas of use include the production of potato products, such as chips or French fries, in the production of baker&#39;s yeast using molasses or other industrial fermentation processes, such as the production of medicaments, to reduce foaming to a level which does not interfere with the industrial production process.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the use of special carbonic acid esters asfoam control agents in the processing and/or production of foods and infermentation processes.

2. Discussion of Related Art

Foam problems can be prevented before the formation of foam by additionof foam inhibitors and after the formation of foam by addition ofdefoamers. In this sense, both foam inhibitors and defoamers are foamcontrol agents.

In the industrial processing and/or production of foods, considerablesignificance is attributed to the control and prevention of foaming. Forexample, in the industrial processing of sugar-containing plant juices,as carried out on an industrial scale in the case of sugar beet,particular difficulties are caused by excessive foaming in thediffusors, in the defecation units, in the carbonizing tanks and in theevaporators. It is also important in the production of potato products,such as chips or pommes frites (French fries), in the production ofbaker's yeast using molasses or other industrial fermentation processes,such as the production of medicaments, to reduce foaming to a levelwhich does not interfere with the industrial production process.

The auxiliaries used to regulate foaming in the sugar industry couldenter the end product, sugar, in traces, so that physiologicallycompletely safe foam control agents are of course essential. Inaddition, foam control agents which enter the wastewater during theexternal beet washing process should be readily bioldegradable.Moreover, the potential residues of foam control agents, which enter themolasses during processing of sugar beet, should not adversely affectyeast production because the molasses thus obtained is used as anutrient in the industrial production of baker's yeast. Where they areused in the potato-processing industry, foam control agents must be atleast capable of regulating the starch foam which is so difficult tocontrol. In practice, foam-suppressing agents are generally expected todevelop a good spontaneous effect and to show a good long-term effect inlow concentrations.

Fats and oils, such as rapeseed oil, peanut oil, olive oil and woolgrease, have long been used for defoaming in the sugar and yeastindustries. Fatty acid monoglycerides, fatty acid polyglycol esters,polyalkylene glycols, ethylene oxide adducts with alkyl phosphoric acidsand with branched alcohols, alkylene oxide adducts with oligosaccharidesand free fatty alcohols have also been proposed for this purpose.Typical foam control agents with patent literature references andpotential applications are described in Ullmanns Enzyklopadie dertechnischen Chemie, Vol. A 11 (5th Edition) 1988, pages 465 to 490.

According to DE-AS 12 42 569, carbonic acid esters in which the alkylgroups may optionally be interrupted by an oxygen atom are used asfoam-suppressing agents for foaming detergent systems containinganionic, cationic and nonionic compounds. The machine washing anddisinfection of bottles and cans in the food industry is mentioned asone possible application. Although the dialkyl carbonates mentioned inthe cited document have a good defoaming effect for this particularapplication, this does not necessarily mean that they are suitable forother applications, including for example the sugar industry, the potatoindustry and fermentation processes and their special requirements.Thus, in the sugar industry for example, totally different substances,such as saponins, are responsible for foaming and, accordingly, alsoinfluence the constitution of the foam generated. In addition, bottlewashing processes differ considerably in their mechanics and, above all,in the introduction of air which in turn impairs the nature and extentand the foam formed.

U.S. Pat. No. 3,332,980 describes alkoxylated carbonic acid esters ofwhich the alkyl radicals have a degree of alkoxylation of 1 to 150 andwhich may be used for various applications. One of the many possibleapplications of these substances includes defoaming in its broadestsense, although the document in question does not mention which of thealkoxylated carbonic acid esters may be used in which quantities forwhich type of defoaming. As explained, however, foams often differconsiderably from one another, so that there was still a need forspecial compounds which would satisfy the above-mentioned requirementsfor use as a foam control agent in the sugar industry, in thepotato-processing industry and/or in fermentation processes.

Accordingly, the problem addressed by the present invention was toprovide new special foam control agents which would show improvedspontaneous and long-term activity in low concentrations and which inaddition would satisfy the requirements for their use in the sugarindustry, in the potato industry and in fermentation processes.

DESCRIPTION OF THE INVENTION

Accordingly, the present invention relates to the use of carbonic acidesters corresponding to general formula I ##STR2## in which R¹ is analkyl radical derived from an aliphatic saturated primary alcoholcontaining 1 to 22 carbon atoms and R² is an alkyl radical derived froman aliphatic, saturated primary alcohol containing 1 to 8 carbon atomsand/or has the same meaning as R^(x) and n is a number of 2 to 20 whilem is 0 or has the same meaning as n, as foam control agents for thesugar beet or potato-processing food industry and/or in fermentationprocesses.

The carbonic acid esters used in accordance with the invention arecompounds known per se and may be prepared by the methods described inHouben Weyl, "Methoden der organisthen Chemie", 4th Edition, Vol. E4,pages 66 st seq. On way of obtaining these compounds is the reaction ofphosgene with aliphatic alcohols which leads to symmetrical carbonicacid esters, cf. J. Chem. Sec. 117, 708 (1920). Another method is thereaction of chloroformic acid esters with alcohols, in which casesymmetrical or asymmetrical carbonic acid esters may be obtainedaccording to the type of reactants used, cf. J. Prakt. Chem. 22, 353(1880). The most simple synthesis is the transesterification of carbonicacid alkyl esters with alcohols in the presence of basic catalysts, suchas sodium methanolate or alkali metal hydroxide, with elimination of themore readily volatile alcohol component. It is possible by thisparticular process to obtain symmetrical and/or asymmetrical carbon acidesters according to the quantity in which the alcohols required for thetransesterification are used.

According to the invention, the carbonic acid esters corresponding togeneral formula I are preferably obtained by transesterification ofdialkyl carbonates with adducts of ethylene oxide and aliphatic,saturated primary alcohols containing 1 to 22 carbon atoms. The dialkylcarbonates suitable for transesterification have two identical aliphaticsaturated alkyl radicals containing 1 to 8 carbon atoms which may bebranched or unbranched. Particularly suitable dialkyl carbonates aredimethyl, diethyl, di-n-propyl, diisopropyl, di-n-butyl, diisobutyl,di-n-octyl or di-2-ethylhexyl carbonate.

To produce the carbonic acid esters corresponding to general formula I,the dialkyl carbonates mentioned are partly or at least substantiallycompletely esterified with adducts of 2 to 20 mol ethylene oxide withaliphatic, saturated primary alcohols containing 1 to 22 carbon atoms.Adducts of 2 to 20 mol ethylene oxide with aliphatic, saturated, primaryunbranched alcohols containing 1 to 22 carbon atoms are preferred.Suitable representatives of these ethoxylated alcohols are adducts of 2to 20 mol ethylene oxide with methanol ethanol, propanol, butanol,pentanol, hexanol, octanol, nonanol, decanol, dodecanol, tetradecanol,hexadecanol, octadecanol, eicosanol and docosanol. Of these, adducts ofethylene oxide with aliphatic, saturated, primary unbranched alcoholscontaining 6 to 20 and, more particularly, 8 to 18 carbon atoms,so-called saturated fatty alcohols, are most particularly preferred. Asusual in oleochemistry, the saturated fatty alcohols containing 8 to 18carbon atoms may be used in the form of the technical mixtures rich inthese fatty alcohols which are obtained in the sodium reduction or inthe catalytic hydrogenation of fatty acid mixtures from the hydrolysisof native fats or oils. The adducts of ethylene oxide with the alcoholsmentioned are produced by known methods carried out at elevatedtemperature and pressure in the presence of suitable ethoxylationcatalysts, such as alkali metal alcoholate or hydrotalcite. 2 to 20 molethylene oxide are reacted per mol alcohol, depending upon the requireddegree of ethoxylation n or m. The following adducts of ethylene oxidewith alcohols are particularly preferred for the production of thecarbonic acid esters of general formula I by transesterification of thedialkyl carbonates: octanol with 4 mol ethylene oxide, octanol with 8mol ethylene oxide, dodecanol with 2 mol ethylene oxide, dodecanol with6 mol ethylene oxide, dodecanol with 7 mol ethylene oxide, tetradecanolwith 2 mol ethylene oxide, tetradecanol with 6 mol ethylene oxide,tetradecanol with 7 mol ethylene oxide, hexadecanol with 2 mol ethyleneoxide, hexadecanol with 7 mol ethylene oxide, octadecanol with 2 molethylene oxide, octadecanol with 7 mol ethylene oxide and/or technicalmixtures thereof.

As already mentioned, the transesterification of the dialkyl carbonateswith the adducts of ethylene oxide and the aliphatic, saturated, primaryC₁₋₂₂ alcohols mentioned may be partial or complete. So-calledsymmetrical carbonic acid esters are obtained by complete or leastsubstantially complete transesterification. One embodiment of thepresent invention is characterized by the use of symmetrical carbonicacid esters corresponding to general formula I in which R² has the samemeaning as the alkyl radical R¹ and R¹ is derived from one of theabove-described adducts of ethylene oxide with aliphatic, saturated,primary C₁₋₂₂ alcohols, so that the indices n and m representing thedegree of ethoxylation stand for the same number. Symmetrical carbonicacid esters corresponding to general formula I, in which R¹ and R²represent the same alkyl radical derived from an aliphatic, saturatedprimary alcohol containing 6 to 20 carbon atoms, preferably fromunbranched alcohols containing 8 to 18 carbon atoms, and n and m standfor the same number of 2 to 20, preferably 2 to 6 and more preferably 2to 12, are most particularly preferred. Symmetrical carbonic acid esterscorresponding to the following formulae

[C₈ H₁₇ O(C₂ H₄ O)₄ ]₂ CO

[C₈ H₁₇ O(C₂ H₄ O)₈ ]₂ CO

[C₁₂ H₂₅ O(C₂ H₄ O)₂ ]₂ CO

[C₁₂ H₂₅ O(C₂ H₄ O)₆ ]₂ CO

[C₁₂ H₂₅ O(C₂ H₄ O)₇ ]₂ CO

[C₁₄ H₂₉ O(C₂ H₄ O)₂ ]₂ CO

[C₁₄ H₂₉ O(C₂ H₄ O)₆ ]₂ CO

[C₁₆ H₃₃ O(C₂ H₄ O)₂ ]₂ CO

[C₁₆ H₃₃ O(C₂ H₄ O)₆ ]² CO

[C₁₈ H₃₇ O(C₂ H₄ O)₂ ]₂ CO

[C₁₈ H₃₇ O(C₂ H₄ O)₆ ]₂ CO and/or technical mixtures thereof areparticularly suitable.

The production of these symmetrical carbonic acid esters used inaccordance with the invention by transesterification requires at least0.5 mol of the dialkyl carbonates mentioned per mol of theabove-mentioned adducts of ethylene oxide with the alcohols mentioned.The dialkyl carbonates are preferably used in quantities of 0.55 mol to1 mol per mol adducts of ethylene oxide with the alcohols mentioned. Inaddition, it is of advantage to carry out the transesterification in thepresence of basic catalysts, preferably sodium methanolate, and toremove the alcohol released from the dialkyl esters by distillation.However, since transesterifications are equilibrium reactions, thesymmetrical carbonic acid esters may contain both unreacted adducts ofethylene oxide with the alcohols mentioned and only partlytransesterified carbonic acid esters as secondary products. If desired,the unreacted ethoxylated alcohols may be removed by phosphogenation.

Another embodiment of the present invention is characterized by the useof carbonic acid esters corresponding to general formula I, in which R²is a saturated aliphatic alkyl radical containing 1 to 8 carbon atomsand may be the same as or different from the alkyl radical R¹ which inturn is derived from one of the aliphatic, saturated, primary C₁₋₂₂alcohols already mentioned. At all events, the indices m and n in thisembodiment differ from one another insofar as m=0 and n is a number of 2to 20 representing the degree of ethoxylation. Of the asymmetricalcarbonic acid esters of general formula I, those in which R² is a methylor ethyl group, R¹ is an alkyl radical derived from an aliphaticsaturated primary C₆₋₂₀ alcohol and preferably from an unbranched C₈₋₁₈alcohol and n is a number of 2 to 16 and preferably 2 to 12 and m=0 aremost particularly preferred. Asymmetrical carbonic acid esterscorresponding to the following formulae

C₈ H₁₇ O(C₂ H₄ O)₄ COOCH₃

C₈ H₁₇ O(C₂ H₄ O)₈ COOCH₃

C₁₂ H₂₅ O(C₂ H₄ O)₂ COOCH₃

C₁₄ H₂₉ O(C₂ H₄ O)₆ COOC₂ H₅

C₁₆ H₃₃ O(C₂ H₄ O)₇ COOC₂ H₅

C₁₈ H₃₇ O(C₂ H₄ O)₂ COOCH₃ and/or technical mixtures thereof areparticularly suitable.

In order to obtain these asymmetrical carbonic acid esters, at least 1mol and preferably 4 mol to 10 mol dimethyl carbonate is used per moladducts of ethylene oxide with the alcohols mentioned. Thetransesterification may otherwise be carried out in the same way asdescribed for the symmetrical carbonic acid esters. However, theasymmetrical carbonic acid esters obtained in this way may again containboth unreacted adducts of ethylene oxide with the described alcohols andpartly symmetrical carbonic acid esters. Mixtures such as these are alsointended to be covered by general formula I for asymmetrical carbonicacid esters. Mixtures of the above-described symmetrical andasymmetrical carbonic acid esters may of course also be used for thepurposes of the invention.

Carbonic acid esters which are liquid at temperatures below 25° C. andpreferably at temperatures below 10° C. are preferred for the purposesof the invention because liquids are more suitable for metering and foroptimal mixing with the material to be defoamed and for thoroughlywetting foam bubbles which have already formed. Solutions of solidcarbonic acid esters corresponding to general formula I in liquidcarbonic acid esters corresponding to general formula I and/or in asolvent may of course also be used, but have the disadvantage that anadditional step is involved in preparing the solutions.

Mixtures of carbonic acid esters corresponding to general formula I withcommercial defoamers and/or foam inhibitors, such as fatty acidmonoglycerides, fatty acid polyglycol esters and/or polyalkyleneglycols, which are liquid at temperatures below 25° C. may also be usedas foam control agents.

The carbonic acid esters used in accordance with the invention may beused in widely varying quantities according to requirements. They areeffective even when added in very small quantities, preferably inquantities below 1% by weight and, more particularly, in quantities of0.001 to 0.8% by weight, based on the material to be defoamed, forexample sugar sirup solutions. Technologically, there is no upper limitto the quantity added. For economic reasons, however, as little foamcontrol agent as possible will be added to the material to be defoamed.

The carbonic acid esters used in accordance with the invention act bothas foam inhibitors and as defoamers and, accordingly, may be addedbefore or after the generation of foam. They have a very goodspontaneous and long-term effect over the entire pH range. In addition,they may readily be removed from the material to be defoamed, dependingon the process conditions, so that they may be used as an auxiliary inthe food industry by virtue of their neutral odor, their neutral tasteand their physiological safeness. Particularly good results are obtainedwhere the carbonic acid esters corresponding to general formula I areused as foam control agents in the processing of sugar beet, for examplein the transport, storage and size-reduction of sugar beet and in theextraction process, or in the production of potato products and/or infermentation processes, more particularly in the production of baker'syeast using molasses.

The biodegradability of the carbonic acid esters according to theinvention is of particular importance.

EXAMPLES A) Production of the carbonic acid esters EXAMPLE 1

4 Mol dimethyl carbonate and 0.5 mol-% sodium methanolate in the form ofa 30% methanol solution were heated under nitrogen to 80° C. and 1 molof a commercial adduct of 2 mol ethylene oxide with I mol of a technicalC₁₂₋₁₄ fatty alcohol mixture (chain distribution 0 to 2% C₁₀ ; 70 to 75%C₁₂ ; 24 to 30% C₁₄ ; 0 to 2% C₁₆) was then added dropwise. The reactionmixture was heated in steps (15° C./h) to 140° C. and kept for another 4hours at a maximum temperature of 140° C. The methanol released andexcess dimethyl carbonate were distilled off. The reaction mixture wasthen stirred for 1 hour at 90° C. with 1% by weight layer silicate(Tonsil®), followed by filtration under suction. An asymmetricalcarbonic acid ester having a residual OH value of 3.1 was obtained.

EXAMPLE 2

1.5 Mol dimethyl carbonate, 0.5 mol-% sodium methanolate in the form ofa 30% methanol solution and 2 mol of a commercial adduct of 2 molethylene oxide with 1 mol of a technical C₁₂₋₁₄ fatty alcohol mixture(for chain distribution, see Example 1) were slowly heated undernitrogen to at most 140° C. (15° C./h) and left at that temperature for1 hour. The methanol released and excess dimethyl carbonate weredistilled off. The reaction mixture was worked up in the same way as inExample 1. A symmetrical carbonic acid esters having a residual OH valueof 29.4 was obtained.

EXAMPLE 3

Dimethyl carbonate, sodium methanolate in the form of a 30% methanolsolution and a commercially available adduct of 6 mol ethylene oxidewith 1 mol of a technical C₁₂₋₁₄ fatty alcohol mixture (for chaindistribution, see above) were reacted and worked up as in Example 2. Asymmetrical carbonic acid ester having a residual OH value of 15 wasobtained.

EXAMPLE 4

0.9 Mol diethyl carbonate and 0.5 mol-% sodium methanolate in the formof a 30% methanol solution and 1 mol of a commercially available adductof 2 mol ethylene oxide with 1 mol of a technical C₁₂₋₁₈ fatty alcoholmixture (chain distribution 0 to 3% C₁₀ ; 48 to 58% C₁₂ ; 19 to 24% C₁₄; 9 to 12% C₁₆ ; 11 to 14% C₁₈ ; 0 to 5% C₂₀) were reacted as in Example2. A symmetrical carbonic acid ester having a residual OH value of 37was obtained.

EXAMPLE 5

Dimethyl carbonate, sodium methanolate in the form of a 30% methanolsolution and a commercially available adduct of 7 mol ethylene oxidewith 1 mol of a technical C₁₂₋₁₈ fatty alcohol mixture (for chaindistribution, see Example 4) were reacted and worked up as in Example 2.A symmetrical carbonic acid ester having a residual OH value of 14 wasobtained.

EXAMPLE 6

4 Mol diethyl carbonate, 0.5 mol-% sodium methanolate in the form of a30% methanol solution and 1 mol of a commercially available adduct of 8mol ethylene oxide with 1 mol technical octanol (chain distribution 0 to2% C₆ ; 94 to 98% C₈ ; 0 to 5% C₁₀) were reacted and worked up as inExample 1. An asymmetrical carbonic acid ester having a residual OHvalue of 3 was obtained.

EXAMPLE 7

The reaction was carried out and the reaction product worked up in thesame way as in Example 6, except that a commercially available adduct of4 mol ethylene oxide with 1 mol of a technical octanol was used. Anasymmetrical carbonic acid ester having a residual OH value of 5.5 wasobtained.

EXAMPLE 8

1.5 Mol diethyl carbonate, 0.5 mol-% sodium methanolate in the form of a30% methanol solution and 2 mol of a commercially available adduct of 4mol ethylene oxide with technical octanol were reacted and worked up asin Example 2. A symmetrical carbonic acid ester having a residual OHvalue of 12 was obtained.

B) Performance tests

110 g sugar sirup (beet tops) and 420 ml water were introduced into a 2liter measuring cylinder. Using a laboratory flow inducer with an outputof 3 liters per minute, the solution was withdrawn from the bottom ofthe measuring cylinder with a glass tube. The liquid was returned by asecond tube of which the lower end was level with the top edge of themeasuring cylinder. When foam and liquid together reached a volume of2000 ml, 0.05 ml of the various foam control agents were added bymicropipette and the total volume of foam height and liquid was read offafter 0.5, 1, 2, 3, 5, 10, 20 and 30 minutes. In this way, the carbonicacid esters of Examples 1 to 8 were tested at various pH values adjustedby addition of potassium hydroxide and at various temperatures. Table Ishows the total volume of liquid and foam height as a function of time,pH value, temperature and the particular foam control agent added.

C) Biological degradability

The ester of Example 4 was tested for its biological degradability bythe Closed Bottle Test and the BODIS Test (total degradation). Thesolubility of the ester was improved by addition of the alkylphenolpolyalkylene glycol ether nonylphenol-10EO-5PO. Ultrasound was appliedfor dispersion.

The ester according to the invention achieved BOD/COD results of >60% inthe CB Test and values of>80% BOD₂₈ /COD in the BODIS Test. Accordingly,the ester may be classified as readily biodegradable.

                                      TABLE I                                     __________________________________________________________________________    Time in minutes after addition of defoamer                                    Foam control                                                                  agent acc.                                                                           Blank                                                                  to Example                                                                           value                                                                             0.5 1  2  3  5  10 20 30 pH Temperature                            __________________________________________________________________________    1      2000                                                                              980 700                                                                              660                                                                              660                                                                              620                                                                              600                                                                              580                                                                              600                                                                              5.5                                                                              23° C.                          2      2000                                                                              1400                                                                              820                                                                              700                                                                              660                                                                              660                                                                              660                                                                              700                                                                              740                                                                              5.5                                                                              23° C.                          3      2000                                                                              640 540                                                                              500                                                                              460                                                                              460                                                                              500                                                                              560                                                                              600                                                                              5.5                                                                              23° C.                          4      2000                                                                              700 660                                                                              640                                                                              620                                                                              580                                                                              580                                                                              620                                                                              640                                                                              5.5                                                                              23° C.                          5      2000                                                                              900 540                                                                              500                                                                              460                                                                              460                                                                              480                                                                              560                                                                              600                                                                              5.5                                                                              23° C.                          6      2000                                                                              520 560                                                                              580                                                                              620                                                                              640                                                                              680                                                                              740                                                                              780                                                                              5.5                                                                              23° C.                          7      2000                                                                              520 500                                                                              520                                                                              560                                                                              600                                                                              640                                                                              680                                                                              720                                                                              5.5                                                                              23° C.                          8      2000                                                                              520 520                                                                              520                                                                              520                                                                              520                                                                              520                                                                              540                                                                              580                                                                              5.5                                                                              23° C.                          8      2000                                                                              520 540                                                                              560                                                                              560                                                                              560                                                                              560                                                                              580                                                                              600                                                                              5.5                                                                              40° C.                          8      2000                                                                              460 440                                                                              440                                                                              440                                                                              440                                                                              460                                                                              500                                                                              500                                                                              11 10° C.                          __________________________________________________________________________

We claim:
 1. In a method of suppressing foaming in the processing ofsugar beets or potatoes or in fermentation processes in the processes orproduction of foods, the improvement comprising using a carbonic acidester corresponding to general formula I: ##STR3## wherein: R¹ is analkyl radical derived from an aliphatic saturated primary alcoholcontaining 1 to 22 carbon atoms;R² is an alkyl radical derived from analiphatic, saturated primary alcohol containing 1 to 8 carbon atomsand/or has the same meaning as R¹ ; n is a number from 2 to 20; and m is0 or has the same meaning as n, in a material to be defoamed and in anamount effective to suppress foaming in said material.
 2. A method asclaimed in claim 1 wherein said carbonic acid ester of general formula Iare liquid at temperatures below 25° C.
 3. A method as claimed in claim1 wherein said carbonic acid ester of general formula I are liquid attemperatures below 10° C.
 4. A method as claimed in claim 1 wherein R²and R¹ represent the same alkyl radical derived from an aliphatic,saturated primary C₆₋₂₀ alcohol, and n and m represent the same numberand are each from 2 to
 16. 5. A method as claimed in claim 4 whereinsaid aliphatic, saturated primary C₆₋₂₀ alcohol is an unbranched C₈₋₈alcohol.
 6. A method as claimed in claim 1 wherein R¹ is an alkylradical derived from an aliphatic, saturated primary C₆₋₂₀ alcohol, R²is a methyl or ethyl radical, n is a number of from 2 to 16, and m is 0.7. A method as claimed in claim 6 wherein said aliphatic, saturatedprimary C₆₋₂₀ alcohol is an unbranched C₈₋₁₈ alcohol.
 8. A method asclaimed in claim 1 wherein said carbonic acid ester of general formula Iare used in quantities below 1% by weight based on the material to bedefoamed.
 9. A method as claimed in claim 1 wherein said carbonic acidester of general formula I are used in quantities of 0.001 to 0.8% byweight, based on the material to be defoamed.
 10. A method as claimed inclaim 1 wherein said method is practiced in the storage, processing, orsize-reduction of sugar beets and in the production of baker's yeastusing molasses.